Jonny Wilkinson has added to England's fitness concerns ahead of their Six Nations match with Ireland by sitting out training today due to a combination of bumps, bruises and a tight right hamstring.

Brian Ashton has called up Mike Catt, the veteran World Cup winner, to his squad as cover, with Toby Flood most likely to step up from the replacements to cover Wilkinson at fly-half. The England head coach has already summoned Harlequins wing David Strettle to the training camp at the University of Bath because Jason Robinson is struggling with a neck injury.

Speaking as the squad flew out from Heathrow to Dublin, ahead of the game at Croke Park, Ashton said "There will be no decisions on Jason and Jonny for at least another 24 hours, when we will assess the situation again."

Catt, of London Irish, has won 67 caps but has not played for England since the second Test against Australia in Melbourne last summer. His last appearance against Ireland was in 2001, when England blew their grand-slam hopes at Lansdowne Road. Flood, 21, has yet to start a Test match.

Robinson, meanwhile, suffered his injury once the training intensified at Bath yesterday, forcing him to watch the remainder of the morning session clutching an ice pack to his neck. His potential replacement, Strettle, may have surprised some as he is uncapped at international level, although his sparkling play has been a feature of his club’s rise up the Guinness Premiership.

It would, though, be a serious disruption were Robinson to withdraw. His return to international rugby and the form he has shown in the two internationals at Twickenham this month have been one of the main positives of Brian Ashton’s brief tenure as head coach. Nor is it only his attacking skills that have been on display. He has been solid in defence, too, and that is a quality that will be much in demand against an Ireland side directed by Ronan O’Gara.

With Olly Morgan, the Gloucester full back, scheduled to play in only his second international, the promotion of Strettle confirms Ashton’s determination to go with form. Morgan was called up from the England Saxons squad when Iain Balshaw was forced out of the opening Six Nations game, against Scotland, and Strettle follows the same route.

At 23, he is in his first Premiership season after joining Harlequins from Rotherham, but has scored nine tries in 14 matches. Strettle has also created openings for colleagues with some electric running, evident when he eluded three tacklers on his way to the line during the Saxons’ victory over Ireland A in Belfast a fortnight ago.

Ashton was not short of options as cover for Robinson, given that Mark Cueto is finding his way back to form with Sale Sharks, and Ben Cohen, of Northampton, played as recently as the autumn internationals. But the head coach will hope that Robinson receives clearance tomorrow.

The Sale captain scored two tries against Scotland and another against Italy before his display in the Premiership encounter with London Wasps last Sunday added to the impression of a man near the height of his powers. He has scored 25 tries in 41 England matches and his work has justified his recall to the side after he reversed his decision, made in 2005, to retire from the international game.

At least Mike Tindall showed in training that he has recovered from the dead leg that forced a premature departure from the match against Italy and the centre should take his place in the refurbished midfield that will challenge Ireland’s settled trio of O'Gara, Gordon D’Arcy and Brian O’Driscoll, the captain.

“The pressure is on,” Wilkinson said yesterday, before announcing his intention to rest today. “We’ve got to find our feet very quickly and understand it’s going to be a frantic pace. It’s going to be one of those games where, if you lose concentration for a second, that could be it.”

There is no shortage of mutual admiration between Wilkinson and O’Driscoll, Lions together in Australia in 2001 and New Zealand in 2005. “Jonny needs to be given time to get back into international rugby,” O’Driscoll said. “Three years in the wilderness will have taken its toll and that’s what made his performance against Scotland [when he scored 27 points on his comeback] remarkable.

“He seemed to have picked up where he left off the last time he was in an England jersey. He controls things so well. He’s massively important to any side he’s played in and I don’t envisage it being any different this time around.”